Overview

PhotoGIF™ is the most powerful tool available for creating optimized GIF and GIF animation files for the web. It uses advanced color reduction and compression technology combined with powerful features not found elsewhere to make producing GIF and GIF animation files easy and efficient.

PhotoGIF™ is an Adobe Photoshop 3.0 File-Format plug-in that integrates seamlessly into Adobe Photoshop. It combines open-and-save simplicity with the most powerful features available for creating GIF and multiple image GIF animation files.


What is GIF?

‘GIF’ stands for the ‘Graphics Interchange Format’ and was developed in 1987 by CompuServe, Inc. to provide a simple, efficient format for the presentation of graphics over the CompuServe on-line service. Because the needs of CompuServe, Inc., when developing the GIF format, closely matched the needs presented by the web, GIF was adopted as the in-line graphic file format for early web browsers. It has since become the primary graphics file format for the web and is supported by all graphical browsers now.

GIF is an ‘indexed color’ format, which uses a palette limited to 256 colors or less. RGB data is stored only in the palette of GIF files, and pixel colors in a GIF image are referenced to the RGB values stored in the palette with one byte indexes into the palette. This means an uncompressed indexed image will be exactly a third as big as an uncompressed RGB image.

In addition to the reduction in image size by the indexed image, GIF is a compressed format and uses ‘lossless’ LZW compression to further reduce the size of the image data in the GIF file.

There are two versions of the GIF format, GIF87a and GIF89a. GIF87a files are based on the original file format specification, while GIF89a files are based on a later revision of the specification which added transparency and multi-image capability to the GIF format. GIF89a is backwards compatible with applications only supporting GIF87a files.


Installing PhotoGIF™

To install PhotoGIF™ simply place the ‘PhotoGIF™’ plug-in inside your Adobe Photoshop ‘Plug-ins’ folder and, optionally, inside the ‘File Formats’ folder within the ‘Plug-ins’ folder. PhotoGIF™ will then be available to use as a method to open and save files the next time Photoshop is restarted. ‘PhotoGIF™’ will then appear as a new item in the file format menu in Photoshop’s open file and save file dialogs.

PhotoGIF™ is a FAT plug-in and will run in native mode on both 68k and PPC based Macintosh computers for best performance.


The PhotoGIF™ Interface

PhotoGIF™ has many capabilities, and its interface is comprised of many different dialogs, unlike most plug-ins that only have one dialog that controls all functions of the plug-in. There are 14 dialogs in PhotoGIF™, 11 of which control the operation of the plug-in. Below is a hierarchy of the dialogs in PhotoGIF™.

• The about box dialogs
	• The preferences
	• The credits
	• The support

• Multi-image open options dialog
	• Open image picker

• Palette options dialogs
	• Palette get file
	• GIF palette picker
	• Color reduction options
	
• The single-image options dialogs
	• Appending get file
	• Appending insertion picker 
	• Multi-image options

Using PhotoGIF™ to perform a ‘Save as...’ on an image minimally requires one dialog, the single-image options dialog, if saving from bitmapped, grayscale, or indexed mode and at most, seven dialogs if saving from RGB mode, loading an existing palette from a multiple image GIF file for color reduction, appending the file being saved to an existing GIF file and resetting the multiple image options for an animation at the same time.